Structures and methods of manufacture for gas diffusion electrodes and electrode components

Abstract

Gas Diffusion Electrodes (GDEs) play a pivotal role in clean energy production as well as in electrochemical processes and sensors. These gas-consuming electrodes are typically designed for liquid electrolyte systems, and are commercially manufactured by hand or in a batch process. However, CDEs using the new electrolytes demand improved electrode structures. This invention pertains to GDEs and gas diffusion media with new structures for systems using membrane electrode assemblies (MEAs), and automated methods of manufacture that lend themselves to continuous mass production. Unexpected improvements in gas and vapor transport through the electrode are realized by incorporating a new dispersion process in the construction, reformulating the applied mix with solution additives, and creating a novel coating structure on a conductive web. Furthermore, combining these changes with a judicious choice in coating methodology allows one to produce these materials in a continuous, automated fashion.

Description

A gas diffusion electrode (GDE) consumes or is depolarized by a gas feed while allowing direct electronic transfer between the solid and gas phase. Together with the electrolyte, the GDE provides a path for ionic transfer, which is just as critical. GDEs are typically constructed from a conductive support, such as a metal mesh, carbon cloth, or carbon paper. This support is often called a web. The web is coated with hydrophobic wet-proofing layers, and finally, a catalytic layer is applied most commonly to one face. While the catalytic layer can consist of very fine particles of a precious metal mixed with a binder, many employ the methods similar to that in Petrow, et al., U.S. Pat. No. 4,082,699. This patent teaches the use of using finely divided carbon particles such as carbon black as the substrate for small (tens of angstroms) particles of the nobel metal. Thus called a "supported" catalyst, this methodology has shown superior performance and utilization of the catalyst in ele...

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